We use the perfective will have when we are looking back from a point in time when something will have happened.

By the end of the decade scientists will have discovered a cure for influenza.
I will phone at six o’clock. He will have got home by then.

or looking "back" from the present:

Look at the time. The match will have started.
It’s half past five. Dad will have finished work.

We use would have as the past tense form of will have:

I phoned at six o’clock. I knew he would have got home by then.
It was half past five. Dad would have finished work.

We use would have in past conditionals to talk about something that did not happen:

If it had been a little warmer we would have gone for a swim.
He would have been very angry if he had seen you.
 

Exercise

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Comments

Hi..I got a doubt
Don't phone them yet, they won't have got up.
why it isn't "wouldn't" in the place of "won't"? Is it because the sentence is in present tense, the verb should be "won't"?
I'm imagining this situation which I'm not sure of whether they are sleeping or not.. So why don't we put wouldn't instead of won't? This question may appear silly. But please clarify my doubt. Thank you sir.

Hello wisefool,

I'm afraid that 'wouldn't' would not be correct here. 'will' (and 'won't') can be used to make predictions about the present when the speaker is certain about what they are saying. In this case, the person who said the sentence you're asking about is showing they are certain that the other people are still asleep.

If you'd like to see a bit more about this, it is explained in the 'Making predictions' section of the Cambridge Dictionary Grammar's page on 'will'.

All the best,
Kirk
The LearnEnglish Team

Hi, I have a doubt regarding the interrogative form of the conditional.

Which one is correct?

"Would you have gone?" or "would have you gone?"

the helping verb should be before the subject to form an interrogative sentence. I'm confused. many people are saying the first sentence is right. Another example

"what have you done?" " what you have done?"

Are both these sentences correct?

the first example is just similar to the second example. but the subject is after "have" Is it not the contradiction? Please clear my confusion. I hope you understood my question. Thank you sir.

Hello wisefool,

When constucting a question we invert only the first helper/auxiliary verb. For example, in this sentence we invert only 'will', not 'have been':

 

He will have been working there for five years soon.

Question: Will he have been working there for five years soon?

 

The pattern is the same for '...would have gone'. Only the first helper verb is inverted.

 

Best wishes,

Peter

The LearnEnglish Team

Hello sir. I have just saw this sentence on an academic article and it got me a little bit confused. "The competitive pressure
may spur local firms to operate more efficiently and introduce new technologies earlier than would
otherwise have been the case."

Now my question is should have the sentence been The competitive pressure
may spur local firms to operate more efficiently and introduce new technologies earlier than would
otherwise be case.

I feel "otherwise it would have been the case" is a sentence about past, but here the author is talking about the future so the sentence should have been completed by " otherwise it would be the case"

Can you please enlighten me, when you have time?

Thank you so much.

Hello M.Kemal,

Using 'be' in this sentence is also correct, but 'have been' is not wrong. Rather than referring to the past here, one can understand it as referring to an imaginary or hypothetical time, i.e. the time that would exist if the competitive pressure did not exist.

All the best,
Kirk
The LearnEnglish Team

hello sir
Can we say: "If it WAS a little warmer we would have gone for a swim.
He would have been very angry if he SAW you."
If we cannot. why?
Thank you.

Hello mohammad bazzy,

Yes, those forms are correct. Some people prefer 'were' instead of 'was' in second conditional sentences such as these, but 'was' is also commonly used with first and third person singular subjects.

All the best,
Kirk
The LearnEnglish Team

Hi! greetings & good-day!
I would like to know the difference between these two sentences. I think both of them have same assumption i.e by the end of the decade research will be finished. I am little bit confused!! please help me. Thanks.

1. By the end of the decade scientists will discover a cure for cancer
2. By the end of the decade scientists will have discovered a cure for cancer

Hello sudhir31,

The difference is more a difference of emphasis than anything. In 2, the fact that the cure has already been discovered is emphasised more than in 1, but that's about it. Although both sentences are fine, I'd say that 2 is more common and would encourage you to use it because the future perfect is very often used with expressions like 'by the end of ...'.

All the best,
Kirk
The LearnEnglish Team

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